The present invention relates to a pretensioner that pulls a seat belt at the time of a rapid deceleration of a vehicle and relates to a seat belt apparatus.
Conventionally, vehicle seats are equipped with seat belt apparatuses for restraining occupants each of which prevents the occupant from being moved forward due to an inertial force when an impact is generated, for example, at the time of a rapid deceleration or a collision of the vehicle. Such a seat belt apparatus is generally provided with an Emergency Locking Retractor (hereinafter, referred to as an ELR) which does not restrain motion of the occupant in normal driving but locks a winding shaft for the seat belt to prevent the seat belt from being further withdrawn only when an impact is generated to the vehicle. The ELR locks the winding shaft within a very short time after detecting a deceleration of a predetermined value or more, thereby preventing the seat belt from being further withdrawn.
However, according to the aforementioned ELR which merely locks the winding shaft, in case where the seat belt is loosely wound onto the winding shaft when worn by the occupant, a certain amount of the seat belt may be withdrawn even when the winding shaft is locked. Even when the seat belt is not loosely wound, the seat belt may still be withdrawn between the time of detection of a deceleration of the predetermined value or more and the time of locking of the winding shaft.
As a device for canceling the looseness of the seat belt and the withdrawal of the seat belt caused by the time lag until the winding shaft is locked to some extent, there is known a pretensioner which pulls the seat belt buckle when a predetermined deceleration is detected disclosed in Japanese Patent Application JP-A-2003-146184 (FIG. 2 and FIG. 4), incorporated by reference herein.
The pretensioner as disclosed in Japanese Patent Application JP-A-2003-146184 comprises a wire of which one end is connected to a seat belt buckle and the other end is fixed to a piston in a cylinder and a housing through which the wire is passed and which supports the cylinder. When a deceleration of the vehicle is detected, high-pressure gas is spouted into a gas chamber formed in the housing so as to move the piston, thereby pulling the wire.
Mounted on the other side of the housing from the cylinder is a holder having a guide hole for guiding the wire toward the cylinder. A protection member (guard pipe) for protecting the wire is disposed inside the gas chamber to cover the outer periphery of the wire and a seal member is disposed on the other side of the housing from the cylinder to seal between the gas chamber and the guide hole of the holder.
The seal member is fixed inside the housing to prevent the seal member from being pulled according to the pulling of the wire during the actuation of the pretensioner. For fixing the seal member inside the housing, generally, a plurality of engaging claws are formed by metallic molding at a plurality of locations in the circumferential direction of the inner wall of the housing and these claws are crimped to hold the seal member.
In some existing pretensioners, engaging claws which are molded as a part of the housing may be crimped to fix the seal member inside the housing. However, when the housing is made of a material having a relatively low ductility, such as a die-cast aluminum alloy, it is difficult to fix the seal member.
When the housing is a die-casting product made of aluminum alloy, reduction in weight of the housing is achieved. However, since the material has a low ductility, it is difficult to efficiently crimp the engaging claws to hold the seal member. That is, it is difficult to fix the seal member inside the housing by crimping the claws.